It seems to be an issue when you have 05 and 08 environments installed and accidentally use 08 feature in the 05 project - VS 05 will start using .net 3.5 behind the scene and silently switch project type to 2008 (!).

You can open it up in 2005 by replacing first two lines in solution file with:

jtentor wrote:
But you say we continue using VS 2005 or it is an option that I can manage changing .sln file.
I think that is a GOOD IDEA TO GO VS 2008

I like VS 2008 too, but not everybody have it and most using shared hosting with .NET 2.0 and won't be happy running into issues with .NET 3.5 features. You still can run it locally on 2008 though, so should be no problem.